Conventionally, mold stators are obtained by injecting a thermosetting resin (hereinafter, “mold resin”) such as a BMC (Bulk Molding Compound) into a mold die that accommodates therein a stator core. For example, in a conventional mold stator described in Patent Literature 1 mentioned below, the horizontal cross-sectional shape of a stator core (the shape of a stator core as viewed planarly) is annular regular hexagonal and outside of the stator core is covered by a mold resin. That is, a plurality of vertexes that are formed so as to radially and outwardly protrude and a plurality of flat surface parts are formed on an outer circumference of the stator core. According to the conventional mold stator described in Patent Literature 1 mentioned below, in order to improve the yield of the stator, the flat surface part is provided on the outer circumference of the stator core.